Thanks Canyon. It is perhaps the water content that is grabbing terpenes because they are definitely soluble in water. Using 190 proof, maybe @ only 5% water, it's not much of a problem. Everyone is chilling the alcohol to (?) prevent it from absorbing the chlorophyll & such (?). So, to clarify that principle, is chilling to cut down on the alcohol picking up the undesirables OR is it to cut down on the water content picking up the undesirables????
I think there is some widespread confusion about water solubility of terpenes and if you surf the web a bit that confusion becomes evident. This is a prime example of taking a stance on an issue and you can definitely find substantiating evidence.
TCI America, an international chemical company states:
"In general, most of the terpenes are insoluble in water but soluble in ethanol, chloroform and diethyl ether."
Steep Hill Labs says terpenes are widely considered nonpolar (not water soluble) but some of the larger, molecularly heavier terpenes can exhibit polar characteristics.
(Having to rely on memory here which sometimes isn't reliable) I think it was a reasearch paper on pub.net that classified terpenes as water soluble only under endothermic conditions; presence of heat and pressure, basically.
Dinafem, in their explanation of steam distillation of terpenes, avers without reservation that terpenes are water soluble. Their reasoning is that the "boiled off" terpenes travel up the distillation stack in conjunction with the steam and enter the condensation chamber simultaneously. They go on to explain that after condensation, the terpenes are easily reclaimed because they're floating on top of the water. If, in the end results, terpenes are found floating on top of water, should this be considered water soluble? Some that are more chemically inclined may be able to shed some light on this.
Now, on to why we chill ethanol. My mentor gave a twofold legitimacy to it.
One, we freeze the material for 24 hrs shaking vigorously a few times. Supposedly, this makes the trichomes very brittle and are easily separated from the plant matter. I've never made dry ice hash but I assume similar principles apply. If we introduced ethanol at a higher temp than that of the material, it would negate part of our chilling effort.
Secondly, at 0 degrees the water content of the ethanol loses much of its ability to absorb the polar elements of the material, i.e. chlorophyll, flavonoids, waxes, etc that can cause unpleasant taste in the final product.